George Lendich wrote:

. One other question I have is. If titanium is not the material to use what
is ?

                      Respectfully, Tony

Good question. One of the steels obviously. Starting with 4130 heat

treated,

shot peened and rolled threads.  Perhaps 4130 is not optimum. Also you

want

to make a distinction between a bolt and a stud. A bolt has exposed

threads

unlike a properly installed stud. Makes a difference if you are putting
a bending load on the stud or bolt. The bending loads come from the long
bolt vibrating in the over size housing bores.

Paul Lamar

Paul,
I guess I will have to look at this for my single rotor, so this discussion
is timely for me.
So I would be happy if someone told me what the current bolts are made of,
and what characteristics I have to look for.

Perhaps 4340 might be a good material,s it is extremely tough.
George ( down under)

I am not sure I understand the reasons why titanium is not good. Unlike
aluminum It has decent fatigue strength.
6-4 titanium alloy  it is almost as strong as 4130 at ~50% weight.  The
only bad feature discussed in literature is bad friction property,
titanium parts freeze very easy. But there is no motion in these bolts.
Could  someone discuss the issue deeper?

Jerzy

According to Vance (retired rocket scientist.) titanium is notch sensitive.
In other words a crack could start at the base of the threads and you would
have no way of detection it without disassembling the engine.

Paul Lamar
 
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